Year
2008
Abstract
Quantitative high resolution gamma-ray spectroscopy is extensively deployed to nondestructively characterize waste containers. Traditionally the assay result is reported as if the activity is uniformly distributed within the matrix and assumes the matrix is homogeneous and fills the container. Deviations form these conditions result in a bias which is traditionally allowed for in an ad hoc fashion by expanding the total measurement uncertainty reported. Detailed experimental study is tedious and hampered by practical problems such as the production of a large number of test cases. For this reason we have elected to use the Monte Carlo technique to investigate some salient aspects of the problem so that a better treatment might be formulated. In this work we concentrate on the measurement of the standard waste box (SWB) in a standard gamma box counter configuration. We explore the impact of non-uniform source distribution, matrix fill height and matrix inhomogeneity by running a large number of scenarios. We show how the reported uncertainty may be reduced when there is reason to believe multiple hot spots are present.